This invention relates to an expandable, collapsible product for use as a window shade and methods and apparatus used in the manufacture thereof.
Known products of this type generally comprise folded sheets with selected folds connected to provide an elongated hollow channel. For example, U.S. Pat. No. 4,450,027 shows a honeycomb material wherein a plurality of elongate tubes are stacked on top of each other and secured by adhesive to provide a hollow window covering.
Similar products are shown in U.S. Pat. Nos. 4,603,072 and 4,631,108. Another type of construction which produces a hollow article is shown in U.S. Pat. No. 4,685,986 wherein two folded sheets are secured together at selected creases to produce the final product. Other disclosures of honeycomb structures may be found in U.S. Pat. Nos. 4,631,217; 4,676,855; 4,677,012 and 4,677,013.
The structure of a honeycomb product is important with respect to the methods and apparatus required for its manufacture. U.S. Pat. No. 4,685,986, describes a manufacturing technique wherein folded sheets of material are advanced toward each other while a centrally-located apparatus attaches selected creases of the two sheets to hold the sheets together and produce the product. U.S. Pat. No. 4,450,027 shows another technique which is to produce a single elongate tube which is wound around itself after adhesive is applied to provide an oblong coil of the hollow tubular element. The ends of the coil are then cut off leaving the center sections as the finished product.